/**
 * https://leetcode-cn.com/problems/reverse-linked-list/
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @return {ListNode}
 */
var reverseList = function(head) {
  let node = new ListNode()
  let _head = head
  while (head.val !== null){

  }
};
